It is very important in the textile industry that yarn strength be determined during a continuous process, i.e., while the yarn is in motion, without causing delays and in a simple manner, so that reliable prediction of the ultimate suitability of the yarn for many applications is possible. The conventional testing procedures for yarn strength are presently less satisfactory because of increasing automation of the textile industry and the ensuing extremely accelerated work rates. Frequently, the yarn-strength test result is available only when the work already has been completed, ruling out anticipatory corrective steps.
Procedures for testing yarn strength are known, for example, from U.S. Pat. No. 4,173,787 and from European patent document A2 0,241,894. They share the drawback that the yarn is tested off-line, that is, outside the continuous yarn processing, and that therefore no correction is possible during the processing. In view of the measurement being by sampling in a laboratory, the data so obtained are subject to doubt.
Another drawback of the known test methods consists in only allowing static yarn tests, which are of subordinate significance to the yarn processor because the yarn is stressed only impulsively, i.e. dynamically in the ensuing stages.